In clinical practice there is a strong need to be able to detect disease in its earliest stages, to predict disease progression, and to implement patient-tailored therapy. Early detection of in particular neoplastic disease (cancer) is critical to ensure favourable treatment of the disease. In spite of numerous advances in medical research, cancer remains a major cause of death worldwide. When patients seek treatment, they are generally exhibiting symptoms of distant metastases, meaning that too often the cancer is detected too late.
Lung, prostate, breast, and colon cancer are the most common tumours, and in order to facilitate appropriate remedial action by surgical resection, radiotherapy, chemotherapy, or other known treatment methods there is a need for rapid and simple methods for the early diagnoses of cancer. The availability of good diagnostic methods for cancer is also important to assess patient responses to treatment, or to assess recurrence due to re-growth at the original site or metastasis.
Several types of cancer markers, such as, for example, oncogene products, growth factors and growth factor receptors, angiogenic factors, proteases, adhesion factors and tumour suppressor gene products, etc, are presently known and are not only considered essential for early diagnosis, but also for differential diagnosis of patients with uncertain clinical abnormalities such as for distinguishing malignant from benign abnormalities; for predicting the likelihood of response in a particular patient with established malignancy to a selected therapeutic method of treatment; and for providing information concerning the risk, presence, status, or future behaviour of the malignancy in a human or animal subject. Currently, the ability to detect and diagnose cancer through the detection of tumour or cancer markers is an area of widespread interest and as a consequence the need exists for reproducible and reliable methods of identifying new and more useful cancer markers in patient specimens.
Glioblastoma is the most common and most aggressive type of primary brain tumor in humans. The disease is difficult to diagnose and even harder to treat due, in part, to the blood-brain barrier that hinders the delivery of therapeutic agents and detection of potentially important diagnostic markers. Diagnostic markers for glioblastoma are available, but are specific for the tumour tissue itself and require a tumour sample.
Improved screening and detection methods are needed in order to detect cancer in an early phase and to follow the progression of the disease. In the case of cancer we are at a state where we do not only need to detect the tumour, but also need to detect it before it has reached a point of no return, where the treatment becomes palliative instead of curative. People at risk, as well as patients with recurring cancer, should be monitored extensively. Furthermore, since tumours can respond differently to different therapeutics, patient stratification is becoming of importance.
Genetic analysis using tumour biopsies has allowed the identification of many mutations that are useful for diagnosis of the cancer as well as for emerging patient stratification strategies. However, a disadvantage of current genetic analysis of tumours is the need for tumour biopsies, which are often impossible to dissect from patients. Furthermore, the use of biopsies is static and does not allow genetic monitoring of tumour progression or recurrence over time. Moreover, many tumours are heterogeneous, resulting in potential false-positive or false-negative genetic characterization of biopsies of such tumours.
Recently, the use of circulating tumour cells for diagnosis and monitoring of tumour progression or recurrence showed the use of blood as a source of tumour-derived material, notably tissue fragments in the form of cells. However, the use of circulating tumour cells is inefficient for most cancers.
In general, a disease marker is defined as a compound of which the concentration is altered, preferably elevated, in a biological fluid from a diseased patient when compared to a normal healthy subject, and which may subsequently be used as a marker compound indicative of a disease. Yet, the identification of specific compounds, for instance proteins, in various body fluids as markers of disease, such as cancer, has been hampered by the lack of suitable techniques therefore.
Also in case of diseases other than cancer, markers may be available that are difficult to detect. This hampers early diagnosis of the disease.
The present invention aims to overcome the problem of the prior art that not all diseased tissues or disease types (e.g. tumours) result in circulating disease cells (e.g. circulating tumour cells). The present invention also aims to overcome the problem that protein markers for detecting diseases such as cancer are difficult to detect. Further, the present invention aims to provide methods that do not require biopsies, and allow extensive monitoring of patients.